This invention relates to an apparatus for adjusting the light projecting angle of a vehicle headlamp. More particularly, the light projecting angle of the headlamp which is installed so as to be inclined with respect to the vehicle body can be changed in multiple steps by remote control from the driver's seat.
In motor vehicles, especially in automobiles, the vehicle body is coupled to the axles with suspension means comprising leaf springs and coiled springs. Therefore, when a heavy load is applied to the front end of the vehicle body (or to the rear end), the body tilts forward (or backward). As a result, the headlamp beam swings vertically. That is, the angle that light projects from the headlamp with respect to the road surface is changed. This in turn reduces the driver's ability to operate the vehicle safely. When the vehicle body is inclined backwards so that the headlamp beam is swung upwards, the driver in another vehicle approaching the vehicle may be dazzled by the headlamp beam.
In order to eliminate the above-described difficulty. Japanese Patent Application (OPI) No. 46733/1986 (the term "OPI" as used herein means an "unexamined published application") discloses a device for adjusting the light projecting angle. According to OPI 46733/1986 in order to correct the light projecting angle of the headlamp, the headlamp is installed so that it can be inclined with respect to the vehicle body, and the light projecting angle thereof is controlled by remote control from the driver's seat. FIG. 1 is a diagram illustrating the light projecting angle adjusting device thus disclosed. In such a device, the position of an operating switch 1, located in the driver's compartment, is changed to adjust the light projection angle of the headlamp (not shown).
This will now be described in greater detail. When the position of the operating switch 1 is changed so that the common terminal 1-0 of the operating switch 1 is connected to a switching terminal 1-5 thereof, current flows in a relay coil RL1 of a drive unit 2 through a slide contact 21d, a conductor pattern 22 and a slide contact 21a. As a result, the common terminal r11c of the normally open and normally closed contact means r11 of the relay coil RL1 is connected to the normal open contact terminal r11a. This in turn allows current to flow in a DC motor 24 in the direction of the arrow A. As a consequence the DC motor 24 is rotated in the forward direction, whereby the lamp drive shaft 25 is turned clockwise in the figure. As the lamp drive shaft 25 is turned clockwise in this manner, the light projecting angle of the head lamp is changed so that the headlamp beam swings upwards. At the same time, the sliding base plate 26 on which the conductor patterns 22 and 23 are formed is turned clockwise. When the slide contact 21d is disconnected from the conductor pattern 22, the relay coil RL1 is deenergized, so that the common terminal r11c of the contact means r11 is disconnected from the normally open contact terminal r11a. That is, the supply of the current to the DC motor 24 is interrupted. As a result, the light projecting angle of the headlamp is set to a certain value where the headlamp beam is swung upwards.
When the operating switch is returned to its original position where the common terminal 1-0 is connected to the switching terminal 1-4, current flows in another relay coil RL2 in the drive unit 2 through a slide terminal 21e, the conductor pattern 23 and a slide contact 21i, so that the common terminal r12c of the normally open and normally closed contact means of the relay coil RL2 is connected to a normally open contact terminal r12a. That is, current flows in the DC motor 24 in the direction of the arrow B to rotate the DC motor 24 in the reverse direction. The lamp drive shaft 25 is thus turned counterclockwise. Thus, the light projecting angle is changed so that the headlamp beam is swung downwards. As is apparent from the above description, with such a light projecting angle adjusting device, as the position of the operating switch is changed, the switching terminals 1-1 through 1-7 are selected one at a time, to change the light projecting angle in seven steps.
However the light projecting angle adjusting device of FIG. 1 suffers from a disadvantage that, as the number of light-projecting-angle adjusting steps increases, the number of lines connecting the operating switch to the drive unit also increases. In the light projecting angle adjusting device shown in FIG. 1, in order to adjust the light projecting angle in seven steps, it is necessary to use seven connecting lines L1 through L7 between the operating switch 1 and the drive unit 2. Since the drive unit 2 is installed along with the headlamp, in the front part of the vehicle body, a relatively large wiring hole, into which the connecting lines are inserted, must be formed in the partition wall between the engine compartment (outside the vehicle) and the driver compartment (inside the vehicle). In other words, as the number of connecting lines between the operating switch and the drive unit increases, the diameter of the wiring hole is increased. This in turn results in an increase in the noise coming from the engine compartment through the wiring hole into the driver compartment.
At the same time, as the number of connecting lines between the operating switch and the drive unit increases, the preVention rain drops or water drops flowing down the connecting lines from the headlamp installed outside the vehicle into the driver compartment becomes considerably more difficult (for instance by inserting the connecting lines respectively into small holes formed in a large diameter bushing). In addition, installation of the connecting lines is also rather difficult and troublesome.